I predicted the UK house price slump of 2007. I was even planning to devote an episode of my BBC2 series to the subject back in 2006, until my producers demanded a different topic. They argued that house prices would assuredly keep rising, so I would seem silly. The replacement theme was “It’s hard to predict the future”; prices duly fell by 15 per cent in real terms.

This triumph should be set in context: I had been forecasting a slump in 2002, 2003, 2004 and 2005. Nevertheless, since Londoners cannot seem to stop discussing the question, “Is there a house price bubble?”, I’ve been trying to figure out the answer, both for Londoners and others.

This isn’t an easy question for economists to answer – bubbles are a matter of psychology, and psychology is not our strong suit. But we can attempt a diagnosis by looking at economic fundamentals. The price of any investment asset should be related to the future income you can derive from that asset, whether it’s the rent you can earn as a landlord, the dividends from corporate shares, or the interest payments on a bond.